Generally, the hull designs of present day watercraft have the disadvantage of relatively slow speed when operating in rough water or swell due to either substantial water resistance from large wetted areas or slamming effects of large waves. This also results in low efficiency and high fuel consumption.
To increase speed and efficiency, various types of hull designs have been developed such as, for example, hydrofoils and water piercing high speed catamarans. Both of these designs raise the main body of the vessel up out of the water to decrease water resistance in rough water and provide shock mitigation caused by slamming waves.
Unfortunately, each of these design concepts have inherent, unfavourable behavioural characteristics. The hydrofoils suffer from cavitation problems affecting maximum speeds and require complex control and drive systems with associated maintenance issues. Surface piercing catamarans have large wetted areas, also limiting maximum speed and suffer from instabilities in pitch in rough water and swells.
U.S. Pat. No. 7,487,736 discloses a hybrid boat hull that comprises two elongated hulls which are curved inwards forming two keel foils. The keel foils provide water displacement when submerged, act in a similar manner to a hydrofoil when piercing through waves and swell and provide a planing capability on the water surface at higher speeds.
It s desirable to provide a foil structure for providing buoyancy and lift to a floating device that has increased stability when encountering waves and when travelling at high speed.
It is also desirable to provide a foil structure for providing buoyancy and lift to a floating device that has increased efficiency.
It is also desirable to provide a foil structure for providing buoyancy and lift to a floating device that is implemented as a retrofit to an existing watercraft.